Electrophysiological studies of primate receptor potentials will focus on the measurement of cone pigment kinetics. Ths proves possible because the only mechanism of adaptation in the photoreceptors at 40 Hz is photopigment bleaching. (This work is being conducted at the Stanford Research Institute.) Psychophysical studies of the minimally distinct border (MDB) are continuing. Stimuli that are equivalent in their border-forming properties appear to plot as lines of chromaticity space and as points along a single helix in MDB space. The properties of these two spaces will be investigated in detail with normal and color deficient observers. (This work is being conducted at the University of California, San Diego.)